Relapsed plasmacytoma in central nervous system after complete remission of extramedullary plasmacytoma

Extramedullary plasmacytoma (EMP) is a rare disease that occurs in 3% to 5% of patients with plasma cell disorder. It occurs most commonly in the upper respiratory tract and the oral cavity. Very few EMP cases have been reported in the central nervous system (CNS). We report herein an unusual case of EMP in the nasal cavity that recurred in the CNS without systemic involvement. A 67-year-old man visited our hospital due to a month-long bout with exophthalmos. He was diagnosed with EMP in the nasal cavity, paranasal sinus, and orbital cavity. He received radiotherapy to which he had complete responses. After 2 years, he visited our hospital because of a month-long headache. He was diagnosed with EMP recurrence in the CNS via brain magnetic resonance imaging and cerebrospinal fluid analysis. He was treated with whole brain radiotherapy and intrathecal chemotherapy with methotrexate, but he expired due to pneumonia.